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The phylogeny of living organisms has changed dramatically in the past few years. As a consequence you will find that different sites may given different, and sometimes conflicting, systematic arrangements for the same group of organisms. No where is this more true than for the "lower organisms", i.e. those groups traditionally treated as bacteria, protozoans, algae and fungi. The traditional older arrangement divided live into two main group; the Monera (bacteria and blue-green algae) and the Eucaryotes (protozoa, algae, plants, fungi, and animals). This older scheme was surplanted by the so-called "Five Kingdom Classification" created by Robert Whittaker. The "Five Kingdom Classification" divided all living organisms into five kingdoms:

Kingdom Monera - Bacteria and blue-green algae

Kingdom Protista - Protozoa and some of the algae

Kingdom Fungi - Fungi

Kingdom Plantae - Plants

Kingdom Animalia - Animals

This division of the living organisms (viruses are ignored as probably not truly living) is the scheme most generally adopted at present and you will find it in many of the sites you visit. However according to recent work there are two fundamental flaws with this system. The first flaw is relatively minor. Certain of the "bacteria" are now recognized to be fundamentally different from the rest of the Monera and probably represent the most primitive characteristics of all living organisms. These organisms have been grouped into a separate kingdom, the Archaea.

The second flaw is most serious. The major division between organisms is between those species without a defined nucleus or organelles such as mitochondria and chloroplasts (equivalent to the Monera of the Five Kingdom scheme) and those groups with a nucleus and organelles (the other four kingdoms of the Five Kingdom Scheme). This fundamental division into two groups are usually termed Procaryotes (Monera of above) and the Eucaryotes (the other four kingdoms). If one adopts this fundamental change as the definition of a kingdom, then we would be left with three kingdoms

Kingdom Archaea

Kingdom Procaryota

Kingdom Eucaryota

A simple modification of the Five Kingdom Scheme would then simply divide the Eucaryota into Protista, Fungi, Plantae, and Animalia at the next lower level. The difficultly, however, it that the group Protista does not really exist. Let me try to explain. The Protista represent a wide variety of different types of organisms representing all of the phylogenetic lines of the Eurcaryotes. Image a wide field of trees, some large, some medium size, and many small. The larger trees, the ones most visible to us, are equivalent to the plants, fungi, and animals. From the standpoint of the biologist, however, all of the trees are equally important and distinct, not just the ones we happen to notice because the species are large and easily seen. The microscopic and the rare are equally important to the systematist. Systematists also have two rules for classifying species into groups; all of the species must have the same ancestoral species (monophyly) and if two groups are of equivalent rank (e.g. phylum, order, family, etc.) one group cannot have an ancestoral species contained in the other (i.e. no paraphyly). If these rules are followed, than all of the currently recognized major groups of the Protista, must have equivalent rank. In other words if the Animalia are treated as a kingdom, then all of the other protist groups (and there are a lot of them) must also be treated as kingdoms. The end result of this strict application of the rules, and new insights into the relationships among the groups, has led to a major upheavel in the classification of the Eucaryotes, particularly among the microscopic groups. No one can seem to agree on the correct levels to assign to each group. In addition there is still a great deal to learn about the relationships among the major groups. Therefore a certain amount of chaos now reigns and will continue to reign until the next great synthesis occurs. It also means that you can expect a certain amount of disagrement between what the various sites on the web will tell you about these relationships.

The classification given below represents an amalgamation of what we consider to be the most up to date viewpoints on the phylogeny of living organisms. However it is tentative and we do not claim it is any better or any worse than other schemes you may see elsewhere on the web. A more technical presentation may be found at the Tree of Life.

Eubacteria (True Bacteria)

Cyanobacteria (Blue-green Algae)

THE "PROTISTS"

Parabasalia

Pelobionta (Pelomyxa)

Diplomonadida

Kinetoplastida (Bodonids and trypanosomes)

Euglenida

Apicomplexa (Apicomplexans)

Ciliata (Ciliates)

Foraminifera

Dinoflagellata (Dinoflagellates)

Radiolaria (Radiolarians)

Chlorophyta (Green algae)

Plant Divisions

Animal and Fungi Divisions

Fungi

Animals and Choanoflagellata

Chromista division (Stramenopiles)

Labyrinthulomycota (Slime nets)

Myxomycota (Slime molds)

Rhodophyta (Red algae)

Bacillariophyta (Diatoms)

Chrysophyta (Golden algae)

Oomycota (Water molds)

Phaeophyta (Kelps and brown algae)

Prymnesiophyta (Coccolithophorids and other haptophytes)

Silicoflagellata (Silicoflagellates)

Testaceafilosea (Testate amoebae)

Xanthophyta (Yellow-green algae)

Trimerophytes

Zosterophylls

NON-VASCULAR PLANTS

DIVISION Hepaticophyta (liverworts)

DIVISION Anthocerotophyta (hornworts)

DIVISION Bryophyta (mosses)

VASCULAR PLANTS

DIVISION Psilotophyta (whisk ferns)

DIVISION Lycophyta (club mosses)

DIVISION Sphenophyta (horsetails)

DIVISION Pterophyta (ferns)

DIVISION Pinophyta (gymnosperms)

SUBDIVISION Cycadicae (cycads)

SUBDIVISION Pinicae

Class Ginkgoatae (Ginkgo)

Class Pinatae (conifers)

SUBDIVISION Gneticae 75

Order Gnetales (Gnetum)

Order Ephedrales (Ephedra)

Order Welwitschiales (Welwitschia)

DIVISION Magnoliophyta (Angiosperms - flowering plants)

Class Magnoliopsida (dicots)

Class Liliopsida (monocots)

 

Chytridiomycota (Chytrids)

Zygomycota (Bread molds)

Ascomycota (Sac and cup fungi, yeasts, mildews)

Basidiomycota (Club fungi, rusts and smuts)

Fungi Imperfectae

"Lichens"

Porifera (Sponges)

Cnidaria (Corals, jellyfish, Hydra)

Ctenophora (Comb jellies)

Platyhelminthes (Flatworms)

Mesosoma (Mesozoans)

Nemertinea (Ribbon Worms)

Rotifera (Rotifers)

Gastrotricha (Gastrotrichs)

Kinorhyncha (Kinorhynchans)

Nematoda (Nematodes)

Nematomorpha (Hair Worms)

Acanthocephala (Acanthocephalan worms)

Entoprocta (Moss Animals)

Priapulida (Priapulids)

Sipuncula (Sipunculids)

Mollusca (Snails, clams, squid, etc.)

Echiura (Spoon worms)

Annelida (Segmented worms)

Tardigrada (Water bears)

Onychophora (Onychophorans)

Pentastomidae (Tongue Worms)

Arthropoda (Crabs, Spiders, Insects, etc.)

Cheliceramorpha (Chelicerates & kin)

Crustaceamorpha (Crustaceans)

Pycnogonida (Sea spiders)

Uniramia (Insects & kin)

Chilopoda (Centipedes)

Diplopoda (Millipedes)

Symphyla (Symphylans)

Pauropoda (Pauropods)

Insecta (Insects)

Brachiopoda (Lamp shells)

Bryozoa (Moss animals)

Phoronida (Horseshoe worms)

Chaetognatha (Arrow worms)

Pogonophora (Bearded tube worms)

Echinodermata (Starfish, sea urchins, sea cucumbers, etc.)

Hemichordata (Acorn worms, graptolites)

Chordata

Urochordata (Tunicates, Sea squirts)

Cephalochordata (Lancelets)

Vertebrata (Vertebrates)